1. Field of the Invention
The present invention relates to a control system for controlling a legged moving robot.
2. Description of the Prior Art
Legged moving robots such as two-legged (biped) locomotion robots may well have a chance to fall down for various reasons because they move by landing and lifting a plurality of movable legs while supporting themselves on a floor with the movable legs, unlike industrial robots that are installed in fixed positions on the floor.
If a legged moving robot is subject to unexpected external forces due to a collision with an object while the legged moving robot is moving or standing still, or is brought out of balance by stepping on an unexpected bump or into a recess while the legged moving robot is moving, then the legged moving robot may fall down because its upper body cannot sufficiently be supported stably on movable legs thereof.
The applicant has proposed a biped locomotion robot which has a function to stabilize its own orientation autonomously (see, for example, Japanese patent application No. 9-33176 or PCT international application PCT/JP98/0399). Even the proposed biped locomotion robot may fall down when it is pushed excessively out of balance by unexpected external forces.
Some legged moving robots have electric actuators combined with respective joints of movable legs and energizable by a battery. If the remaining capacity of the battery becomes too low, then the battery fails to energize the electric actuators and hence to move the movable legs as required, and the robot tends to fall down.
If actuators for movable legs fail or sensors for controlling operation of such actuators fail while the legged moving robot is in operation, then the actuators and hence the movable legs fail to operate as required, resulting in a fall of the robot.
For the reasons described above, it is possible for the legged moving robots to fall down. Since the legged moving robots are generally heavy, when they fall down, they tend to be damaged or they tend to cause damage to an object that is hit by the robots. Particularly, inasmuch as the upper body of a biped locomotion robot is relatively high in position when it is moving or standing still, the damage which the robot or an object hit thereby suffers when the robot turns over is liable to be substantial.
Therefore, it is desirable for legged moving robots to minimize any damage which the robot or an object hit thereby suffers when the robot turns over.